Abstract:

A mobile communication technology, and, more particularly, a method for
efficiently transmitting data stored in a message 3 (Msg3) buffer and a
user equipment for the same is disclosed. The method of transmitting data
by a user equipment in uplink includes receiving an uplink (UP) Grant
signal from a base station on a specific message, determining whether
there is data stored in a message 3 (Msg3) buffer when receiving the UL
Grant signal on the specific message, determining whether the specific
message is a random access response message, and transmitting the data
stored in the Msg3 buffer to the base station using the UL Grant signal
received on the specific message, if there is data stored in the Msg3
buffer when receiving the UL Grant signal on the specific message and the
specific message is the random access response message.

Claims:

1. A method of transmitting data by a user equipment through an uplink,
the method comprising:receiving an uplink grant (UL Grant) signal from a
base station on a specific message;determining whether there is data
stored in a message 3 (Msg3) buffer when receiving the UL Grant signal on
the specific message;determining whether the specific message is a random
access response message; andtransmitting the data stored in the Msg3
buffer to the base station using the UL Grant signal received on the
specific message, if there is data stored in the Msg3 buffer when
receiving the UL Grant signal on the specific message and the specific
message is the random access response message.

2. The method according to claim 1, further comprising:transmitting new
data to the base station in correspondence with the UL Grant signal
received on the specific message, if there is no data stored in the Msg3
buffer when receiving the UL Grant signal on the specific message or the
specific message is not the random access response message.

3. The method according to claim 2, wherein the transmitting the new data
to the base station includes:acquiring a Medium Access Control Protocol
Data Unit (MAC PDU) from a multiplexing and assembly entity;
andtransmitting the MAC PDU to the base station.

4. The method according to claim 2, wherein the UL Grant signal received
on the specific message is a UL Grant signal received on a Physical
Downlink Control Channel (PDCCH), andwherein the user equipment transmits
new data in correspondence with the UL Grant signal received on the
PDCCH.

5. The method according to claim 1, wherein the data stored in the Msg3
buffer is a Medium Access Control Protocol Data Unit (MAC PDU) including
a user equipment identifier.

6. The method according to claim 5, wherein the data stored in the Msg3
buffer further includes information about a buffer status report (BSR) if
the user equipment starts a random access procedure for the BSR.

7. A user equipment comprising:a reception module receiving an uplink
grant (UL Grant) signal from a base station on a specific message;a
transmission module transmitting data to the base station using the UL
Grant signal received on the specific message;a message 3 (Msg3) buffer
storing UL data to be transmitted in a random access procedure; anda
Hybrid Automatic Repeat Request (HARQ) entity determining whether there
is data stored in the Msg3 buffer when the reception module receives the
UL Grant signal and the specific message is a random access response
message, acquiring the data stored in the Msg3 buffer if there is data
stored in the Msg3 buffer when the reception module receives the UL Grant
signal and the specific message is the random access response message,
and controlling the transmission module to transmit the data stored in
the Msg3 buffer to the base station using the UL Grant signal received by
the reception module on the specific message.

8. The user equipment according to claim 7, further comprising a
multiplexing and assembly entity used for transmission of new
data,wherein the HARQ entity acquires the new data to be transmitted from
the multiplexing and assembly entity if there is no data stored in the
Msg3 buffer when the reception module receives the UL Grant signal on the
specific message or the received message is not the random access
response message, and controls the transmission module to transmit the
new data acquired from the multiplexing and assembly entity using the UL
Grant signal received by the reception module on the specific message.

9. The user equipment according to claim 8, further comprising:one or more
HARQ processes; andHARQ buffers respectively corresponding to the one or
more HARQ processes,wherein the HARQ entity transfers the data acquired
from the multiplexing and assembly entity or the Msg3 buffer to a
specific HARQ process of the one or more HARQ processes and controls the
specific HARQ process to transmit the data acquired from the multiplexing
and assembly entity or the Msg3 buffer through the transmission module.

10. The user equipment according to claim 9, wherein, when the specific
HARQ process transmits the data stored in the Msg3 buffer through the
transmission module, the data stored in the Msg3 buffer is controlled to
be copied into a specific HARQ buffer corresponding to the specific HARQ
process, and the data copied into the specific HARQ buffer is controlled
to be transmitted through the transmission module.

11. The user equipment according to claim 8, wherein the UL Grant signal
received by the reception module on the specific message is a UL Grant
signal received on a Physical Downlink Control Channel (PDCCH),
andwherein the HARQ entity controls new data to be transmitted in
correspondence with the received UL Grant signal received on the PDCCH.

12. The user equipment according to claim 7, wherein the UL Grant signal
received by the reception module on the specific message is a UL Grant
signal received on a random access response message received on Physical
Downlink Shared Channel (PDSCH), andwherein the HARQ entity controls the
data stored in the Msg3 buffer to be transmitted using the UL Grant
signal received on the random access response message if there is data
stored in the Msg3 buffer when the reception module receives the UL Grant
signal on the random access response message.

13. The user equipment according to claim 7, wherein the data stored in
the Msg3 buffer is a Medium Access Control Protocol Data Unit (MAC PDU)
including a user equipment identifier.

Description:

CROSS REFERENCE TO RELATED APPLICATIONS

[0001]This application claims the benefit of U.S. Provisional Application
No. 61/087,988, filed on Aug. 11, 2008, which is hereby incorporated by
reference as if fully set forth herein.

[0002]This application claims the benefit of Korean Patent Application No.
10-2009-0057128, filed on May 21, 2009, which is hereby incorporated by
reference as if fully set forth herein.

BACKGROUND OF THE INVENTION

[0003]1. Field of the Invention

[0004]The present invention relates to a mobile communication technology,
and more particularly, to a method for efficiently transmitting data
stored in a message 3 (Msg3) buffer and a user equipment for the same.

[0005]2. Discussion of the Related Art

[0006]As an example of a mobile communication system to which the present
invention is applicable, a 3rd Generation Partnership Project Long
Term Evolution (3GPP LTE) communication system will be schematically
described.

[0007]FIG. 1 is a schematic view showing the network architecture of an
Evolved Universal Mobile Telecommunication System (E-UMTS) as an example
of a mobile communication system.

[0008]The E-UMTS is evolved from the existing UMTS and has been currently
standardized in the 3GPP. Generally, the E-UMTS may be called an LTE
system.

[0009]An E-UMTS network may be largely divided into an Evolved UMTS
Terrestrial Radio Access Network (E-UTRAN) 101 and a Core Network (CN)
102. The E-UTRAN 101 may include a User Equipment (UE) 103, a base
station (hereinafter, referred to as an "eNode B" or "eNB") 104, and an
Access Gateway (AG) 105 positioned at the end of the network and
connected to an external network. The AG 105 may be divided into a
portion for processing user traffic and a portion for processing control
traffic. At this time, an AG for processing new user traffic and an AG
for processing control traffic may communicate with each other using a
new interface.

[0010]One or more cells may exist in one eNode B. A plurality of eNode Bs
may be connected by an interface for transmitting the user traffic or
control traffic. The CN 102 may include the AG 105 and a node for
registering a user of the UE 103. An interface for distinguishing between
the E-UTRAN 101 and the CN 102 may be used.

[0011]Layers of radio interface protocol between the UE and the network
may be classified into a first layer L1, a second layer L2 and a third
layer L3 based on three lower layers of an Open System Interconnection
(OSI) reference model that is widely known in the field of communication
systems. A physical layer belonging to the first layer provides an
information transfer service using a physical channel. A Radio Resource
Control (RRC) layer belonging to the third layer serves to control radio
resources between the UE and the network. The UE and the network exchange
an RRC message via the RRC layer. The RRC layer may be distributed and
located at network nodes of the eNode B 104 and the AG 105.
Alternatively, the RRC layer may be located at only the eNode B 104 or
the AG 105.

[0012]FIGS. 2 and 3 show the structures of radio interface protocols
between the UE and the UTRAN based on a 3GPP radio access network
standard.

[0013]The radio interface protocols of FIGS. 2 and 3 are horizontally
formed of a physical layer, a data link layer and a network layer. The
radio interface protocols are vertically formed of a user plane for
transmitting data information and a control plane for transmitting
control signals. In detail, FIG. 2 shows the layers of a radio protocol
control plane and FIG. 3 shows the layers of a radio protocol user plane.
The protocol layers of FIGS. 2 and 3 may be divided into a first layer
(L1), a second layer (L2) and a third layer (L3) based on three lower
layers of an OSI reference model that is widely known in the field of
communication systems.

[0014]Hereinafter, the layers of the control plane of the radio protocol
of FIG. 2 and the user plane of the radio protocol of FIG. 3 will be
described.

[0015]A physical (PHY) layer of the first layer provides an information
transfer service to an upper layer using a physical channel. The PHY
layer is connected to an upper layer, such as a Medium Access Control
(MAC) layer, via a transport channel. Data is transferred between the MAC
layer and the PHY layer via the transport channel. At this time, the
transport channel is largely divided into a dedicated transport channel
and a common transport channel, depending on whether or not a channel is
shared. Data is also transferred between different PHY layers, such as a
physical layer of a transmitting side and a physical layer of a receiving
side, via a physical channel using radio resources.

[0016]Various layers exist in the second layer. First, the MAC layer
serves to map various logical channels to various transport channels and
serves to multiplex several logical channels into one transport channel.
The MAC layer is connected to a Radio Link Control (RLC) layer, which is
an upper layer, by the logical channel. The logical channel may be
largely divided into a control channel for transmitting information about
the control plane and a traffic channel for transmitting information
about the user plane according to the kinds of information transmitted.

[0017]The RLC layer of the second layer serves to segment and concatenate
data received from an upper layer so as to adjust data size such that a
lower layer transmits data in a radio section. In addition, the RLC
provides three modes, namely, a Transparent Mode (TM), an Unacknowledged
Mode (UM) and an Acknowledged Mode (AM) in order to guarantee various
Quality of Services (QoSs) requested by Radio Bearers (RBs). In
particular, the AM RLC performs a retransmission function using an
Automatic Repeat and Request (ARQ) function for reliable data
transmission.

[0018]A Packet Data Convergence Protocol (PDCP) layer of the second layer
performs a header compression function to reduce the size of an Internet
Protocol (IP) packet header that includes unnecessary control information
and has a relatively large size, for effective transmission in a radio
section having a relatively small bandwidth when transmitting an IP
packet such as an IPv4 packet or an IPv6 packet. Therefore, only
necessary information in a header portion of data is transmitted so as to
improve transmission efficiency of the radio section. In the LTE system,
the PDCP layer also performs a security function, which includes
ciphering for preventing data from being intercepted by a third party and
integrity protection for preventing data from being handled by a third
party.

[0019]A Radio Resource Control (RRC) located at a highest portion of the
third layer is defined only in the control plane. The RRC layer handles
logical channels, transport channels and physical channels for the
configuration, re-configuration and release of RBs. Here, the RBs refer
to logical paths provided by the first and second layers of the radio
protocol, for data transfer between the UE and the UTRAN, and the
configuration of the RBs refers to a process of defining the
characteristics of the radio protocol layer and channel necessary for
providing a specific service, and setting detailed parameters and
operation methods. Each of the RBs is divided into a signaling RB and a
data RB. The SRB is used as a path for transmitting an RRC message in the
control plane (C-plane), and the DRB is used as a path for transmitting
user data in the user plane (U-plane).

[0020]Downlink transport channels for transmitting data from a network to
a UE may include a Broadcast Channel (BCH) for transmitting system
information and a downlink Shared Channel (SCH) for transmitting user
traffic or a control message. The traffic or the control message of a
downlink multicast or broadcast service may be transmitted via the
downlink SCH or via a separate Downlink Multicast Channel (MCH). Uplink
transport channels for transmitting data from a UE to a network may
include a Random Access Channel (RACH) for transmitting an initial
control message and an uplink SCH for transmitting user traffic or a
control message.

[0021]Downlink physical channels for transmitting information transferred
via the downlink transport channels in a radio section between a network
and a UE may include a Physical Broadcast Channel (PBCH) for transmitting
information about a BCH, a Physical Multicast Channel (PMCH) for
transmitting information about an MCH, a Physical Downlink Shared Channel
(PDSCH) for transmitting information about a PCH and a downlink SCH, and
a Physical Downlink Control Channel (PDCCH) (also referred to as a DL
L1/L2 control channel) for transmitting control information provided by
the first layer and the second layer, such as downlink (DL) or uplink
(UL) scheduling grant information. Uplink physical channels for
transmitting information transferred via the uplink transport channels in
a radio section between a network and a UE may include a Physical Uplink
Shared Channel (PUSCH) for transmitting information about an uplink SCH,
a Physical Random Access Channel (PRACH) for transmitting information
about an RACH, and a Physical Uplink Control Channel (PUCCH) for
transmitting control information provided by the first layer and the
second layer, such as a HARQ ACK or NACK, a Scheduling Request (SR), a
Channel Quality Indicator (CQI) report.

[0022]Hereinafter, a random access procedure provided by an LTE system
will be schematically described based on the above description.

[0023]First, a UE performs the random access procedure in the following
cases.

[0024]when the UE performs initial access because there is no RRC
Connection with an eNode B,

[0025]when the UE initially accesses a target cell in a handover
procedure,

[0026]when the random access procedure is requested by a command of an
eNode B,

[0027]when there is uplink data transmission in a situation where uplink
time synchronization is not aligned or where a specific radio resource
used for requesting radio resources is not allocated, and

[0028]when a recovery procedure is performed in case of radio link failure
or handover failure.

[0029]In the LTE system, there are provided two procedures in selecting a
random access preamble: one is a contention based random access procedure
in which the UE randomly selects one preamble within a specific group for
use, and another is a non-contention based random access procedure in
which the UE uses a random access preamble allocated only to a specific
UE by the eNode B. The non-contention based random access procedure may
be used only in the handover procedure or when it is requested by the
command of the base station, as described above.

[0030]A random access procedure of a UE with a specific eNode B may
largely include (1) a step of, at the UE, transmitting a random access
preamble to the eNode B (hereinafter, referred to as a "message 1"
transmitting step if such use will not lead to confusion), (2) a step of
receiving a random access response from the eNode B in correspondence
with the transmitted random access preamble (hereinafter, referred to as
a "message 2" receiving step if such use will not lead to confusion), (3)
a step of transmitting an uplink message using the information received
by the random access response message (hereinafter, referred to as a
"message 3" transmitting step if such use will not lead to confusion),
and (4) a step of receiving a message corresponding to the uplink message
from the eNode B (hereinafter, referred to as a "message 4" receiving
step if such use will not lead to confusion).

[0031]In the random access procedure, the UE stores data to be transmitted
via the message 3 in a message 3 (Msg3) buffer and transmits the data
stored in the msg3 buffer in correspondence with the reception of an
Uplink (UL) Grant signal. The UL Grant signal indicates information about
uplink radio resources which may be used when the UE transmits a signal
to the eNode B, and is received on a random access response message
received on a PDCCH or a PUSCH in the LTE system. According to the
current LTE system standard, it is defined that, if the UL Grant signal
is received in a state in which data is stored in the Msg3 buffer, the
data stored in the Msg3 buffer is transmitted regardless of the reception
mode of the UL Grant signal. As described above, if the data stored in
the Msg3 buffer is transmitted in correspondence with the reception of
all UL Grant signals, problems may occur. Accordingly, there is a need
for research to solve such problems.

SUMMARY OF THE INVENTION

[0032]Accordingly, the present invention is directed to a data
transmission method and a user equipment for the same that substantially
obviate one or more problems due to limitations and disadvantages of the
related art.

[0033]An object of the present invention is to provide a data transmission
method and a user equipment for the same, which is capable of solving a
problem which may occur when data stored in a message 3 (Msg3) buffer is
transmitted according to a reception mode of an Uplink (UL) Grant signal.

[0034]Additional advantages, objects, and features of the invention will
be set forth in part in the description which follows and in part will
become apparent to those having ordinary skill in the art upon
examination of the following or may be learned from practice of the
invention. The objectives and other advantages of the invention may be
realized and attained by the structure particularly pointed out in the
written description and claims hereof as well as the appended drawings.

[0035]To achieve these objects and other advantages and in accordance with
the purpose of the invention, as embodied and broadly described herein, a
method of transmitting data by a user equipment through an uplink
includes receiving an uplink grant (UL Grant) signal from a base station
on a specific message, determining whether there is data stored in a
message 3 (Msg3) buffer when receiving the UL Grant signal on the
specific message, determining whether the specific message is a random
access response message, and transmitting the data stored in the Msg3
buffer to the base station using the UL Grant signal received on the
specific message, if there is data stored in the Msg3 buffer when
receiving the UL Grant signal on the specific message and the specific
message is the random access response message.

[0036]If there is no data stored in the Msg3 buffer when receiving the UL
Grant signal on the specific message or the specific message is not the
random access response message, new data may be transmitted to the base
station in correspondence with the UL Grant signal received on the
specific message.

[0037]The UL Grant signal received on the specific message may be a UL
Grant signal received on a Physical Downlink Control Channel (PDCCH). In
this case, the user equipment may transmit new data in correspondence
with the UL Grant signal received on the PDCCH.

[0038]The UL Grant signal received on the specific message may be a UL
Grant signal received on a random access response message received on
Physical Downlink Shared Channel (PDSCH). In this case, if there is data
stored in the Msg3 buffer when receiving the UL Grant signal on the
random access response message, the user equipment may transmit the data
stored in the buffer in the Msg3 buffer using the UL Grant signal
received on the random access response message.

[0039]The data stored in the Msg3 buffer may be a Medium Access Control
Protocol Data Unit (MAC PDU) including a user equipment identifier, and
the data stored in the Msg3 buffer further include information about a
buffer status report (BSR) if the user equipment starts the random access
procedure for the BSR.

[0040]In another aspect of the present invention, a user equipment
includes a reception module receiving an uplink grant (UL Grant) signal
from a base station on a specific message, a transmission module
transmitting data to the base station using the UL Grant signal received
on the specific message, a message 3 (Msg3) buffer storing UL data to be
transmitted in a random access procedure, and a Hybrid Automatic Repeat
Request (HARQ) entity determining whether there is data stored in the
Msg3 buffer when the reception module receives the UL Grant signal and
the specific message is a random access response message, acquiring the
data stored in the Msg3 buffer if there is data stored in the Msg3 buffer
when the reception module receives the UL Grant signal and the specific
message is the random access response message, and controlling the
transmission module to transmit the data stored in the Msg3 buffer to the
base station using the UL Grant signal received by the reception module
on the specific message.

[0041]The user equipment may further include a multiplexing and assembly
entity used for transmission of new data. In this case, the HARQ entity
may acquire the new data to be transmitted from the multiplexing and
assembly entity if there is no data stored in the Msg3 buffer when the
reception module receives the UL Grant signal on the specific message or
the received message is not the random access response message, and
control the transmission module to transmit the new data acquired from
the multiplexing and assembly entity using the UL Grant signal received
by the reception module on the specific message.

[0042]The user equipment may further include one or more HARQ processes,
and HARQ buffers respectively corresponding to the one or more HARQ
processes. In this case, the HARQ entity may transfer the data acquired
from the multiplexing and assembly entity or the Msg3 buffer to a
specific HARQ process of the one or more HARQ processes and control the
specific HARQ process to transmit the data acquired from the multiplexing
and assembly entity or the Msg3 buffer through the transmission module.

[0043]When the specific HARQ process transmits the data stored in the Msg3
buffer through the transmission module, the data stored in the Msg3
buffer may be controlled to be copied into a specific HARQ buffer
corresponding to the specific HARQ process, and the data copied into the
specific HARQ buffer may be controlled to be transmitted through the
transmission module.

[0044]The UL Grant signal received by the reception module on the specific
message may be a UL Grant signal received on a Physical Downlink Control
Channel (PDCCH). In this case, the HARQ entity may control new data to be
transmitted in correspondence with the received UL Grant signal received
on the PDCCH.

[0045]The UL Grant signal received by the reception module on the specific
message may be a UL Grant signal received on a random access response
message received on Physical Downlink Shared Channel (PDSCH), and the
HARQ entity may control the data stored in the Msg3 buffer to be
transmitted using the UL Grant signal received on the random access
response message if there is data stored in the Msg3 buffer when the
reception module receives the UL Grant signal on the random access
response message.

[0046]According to the above-described embodiments of the present
invention, it is possible to transmit data stored in a Msg3 buffer
according to a reception mode of a UL Grant signal, without confusion.

[0047]It is to be understood that both the foregoing general description
and the following detailed description of the present invention are
exemplary and explanatory and are intended to provide further explanation
of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0048]The accompanying drawings, which are included to provide a further
understanding of the invention and are incorporated in and constitute a
part of this application, illustrate embodiment(s) of the invention and
together with the description serve to explain the principle of the
invention. In the drawings:

[0049]FIG. 1 is a schematic view showing the network architecture of an
Evolved Universal Mobile Telecommunication System (E-UMTS) as an example
of a mobile communication system;

[0050]FIGS. 2 and 3 are views showing the structures of radio interface
protocols between a user equipment (UE) and a UMTS Terrestrial Radio
Access Network (UTRAN) based on a 3rd Generation Partnership Project
(3GPP) radio access network standard;

[0051]FIG. 4 is a view illustrating an operating procedure of a UE and a
base station (eNode B) in a non-contention based random access procedure;

[0052]FIG. 5 is a view illustrating an operating procedure of a UE and an
eNode B in a contention based random access procedure;

[0054]FIG. 7 is a view illustrating a method of transmitting a message 3
in a random access procedure when uplink radio resources are requested;

[0055]FIG. 8 is a view illustrating a problem which may occur when data
stored in a message 3 buffer is transmitted by an Uplink (UL) Grant
signal received on a message other than a random access response message;

[0056]FIG. 9 is a flowchart illustrating a method of transmitting uplink
data by a UE according to a preferred embodiment of the present
invention;

[0057]FIG. 10 is a view illustrating a method of transmitting uplink data
when a Buffer status Report (BSR) is triggered in a UE, according to an
embodiment of the present invention; and

[0058]FIG. 11 is a schematic view showing the configuration of a UE
according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0059]Hereinafter, the preferred embodiments of the present invention will
be described with reference to the accompanying drawings. It is to be
understood that the detailed description which will be disclosed along
with the accompanying drawings is intended to describe the exemplary
embodiments of the present invention, and is not intended to describe a
unique embodiment which the present invention can be carried out.
Hereinafter, the detailed description includes detailed matters to
provide full understanding of the present invention. However, it will be
apparent to those skilled in the art that the present invention can be
carried out without the detailed matters. For example, the following
description will be made on the assumption that a mobile communication
system is a 3rd Generation Partnership Project Long Term Evolution
(3GPP LTE) system, but the present invention is applicable to other
mobile communication systems excluding the 3GPP LTE system.

[0060]In some instances, well-known structures and devices are omitted in
order to avoid obscuring the concepts of the present invention and the
important functions of the structures and devices are shown in block
diagram form. The same reference numbers will be used throughout the
drawings to refer to the same or like parts.

[0061]In the following description, it is assumed that a terminal includes
a mobile or fixed user end device such as a user equipment (UE) and a
mobile station (MS), and a base station includes a node of a network end
communicating with a terminal, such as a Node-B, an eNode B, and a base
station.

[0062]As described above, in the following description, a problem which
may occur when data stored in a message 3 (Msg3) buffer is transmitted
according to a reception mode of an Uplink (UL) Grant signal will be
described in detail and a method of solving the problem will be
described. Transmission and reception of a signal using a random access
procedure and a Hybrid Automatic Repeat Request (HARQ) scheme will be
described in detail.

[0063]FIG. 4 is a view illustrating an operating procedure of a terminal
(UE) and a base station (eNode B) in a non-contention based random access
procedure.

[0064](1) Random Access Preamble Assignment

[0065]As described above, a non-contention based random access procedure
may be performed (1) in a handover procedure and (2) when the random
access procedure is requested by a command of an eNode B. Even in these
cases, a contention based random access procedure may be performed.

[0066]First, it is important that a specific random access preamble
without the possibility of collision is received from the eNode B, for
the non-contention based random access procedure. Methods of receiving
the random access preamble may include a method using a handover command
and a method using a Physical Downlink Control Channel (PDCCH) command.
The UE receives an assigned random access preamble (S401).

[0067](2) Message 1 Transmission

[0068]The UE transmits the preamble to the eNode B after receiving the
assigned random access preamble from the eNode B as described above
(S402).

[0069](3) Message 2 Transmission

[0070]The UE attempts to receive a random access response within a random
access response reception window indicated by the eNode B through a
handover command or system information after transmitting the random
access preamble in step S402 (S403). More specifically, the random access
response information may be transmitted in the form of a Medium Access
Control (MAC) Packet Data Unit (PDU), and the MAC PDU may be transferred
via a Physical Downlink Shared Channel (PDSCH). In addition, the UE
preferably monitors the PDCCH in order to enable to the UE to properly
receive the information transferred via the PDSCH. That is, the PDCCH may
preferably include information about a UE that should receive the PDSCH,
frequency and time information of radio resources of the PDSCH, a
transfer format of the PDSCH, and the like. Here, if the PDCCH has been
successfully received, the UE may appropriately receive the random access
response transmitted on the PDSCH according to information of the PDCCH.
The random access response may include a random access preamble
identifier (e.g. Random Access-Radio Network Temporary Identifier
(RA-RNTI)), an UL Grant indicating uplink radio resources, a temporary
C-RNTI, a Time Advance Command (TAC), and the like.

[0071]As described above, the reason why the random access response
includes the random access preamble identifier is because a single random
access response may include random access response information of at
least one UE and thus it is reported to which UE the UL Grant, the
Temporary C-RNTI and the TAC are valid. In this step, it is assumed that
the UE selects a random access preamble identifier matched to the random
access preamble selected by the UE in step S402.

[0072]In the non-contention based random access procedure, it is
determined that the random access procedure is normally performed, by
receiving the random access response information, and the random access
procedure may be finished.

[0073]FIG. 5 is a view illustrating an operating procedure of a UE and an
eNode B in a contention based random access procedure.

[0074](1) Message 1 Transmission

[0075]First, the UE may randomly select a single random access preamble
from a set of random access preambles indicated through system
information or a handover command, and select and transmit a Physical
Random Access Channel (PRACH) capable of transmitting the random access
preamble (S501).

[0076](2) Message 2 Reception

[0077]A method of receiving random access response information is similar
to the above-described non-contention based random access procedure. That
is, the UE attempts to receive its own random access response within a
random access response reception window indicated by the eNode B through
the system information or the handover command, after the random access
preamble is transmitted in step S501, and receives a Physical Downlink
Shared Channel (PDSCH) using random access identifier information
corresponding thereto (S502). Accordingly, the UE may receive a UL Grant,
a Temporary C-RNTI, a TAC and the like.

[0078](3) Message 3 Transmission

[0079]If the UE has received the random access response valid for the UE,
the UE may process all of the information included in the random access
response. That is, the UE applies the TAC, and stores the temporary
C-RNTI. In addition, data which will be transmitted in correspondence
with the reception of the valid random access response may be stored in a
Msg3 buffer. A process of storing the data in the Msg3 buffer and
transmitting the data will be described later with reference to FIG. 7.

[0080]The UE uses the received UL Grant so as to transmit the data (that
is, the message 3) to the eNode B (S503). The message 3 should include a
UE identifier. In the contention based random access procedure, the eNode
B may not determine which UEs are performing the random access procedure,
but later the UEs should be identified for contention resolution.

[0081]Here, two different schemes for including the UE identifier may be
provided. A first scheme is to transmit the UE's cell identifier through
an uplink transmission signal corresponding to the UL Grant if the UE has
already received a valid cell identifier allocated by a corresponding
cell prior to the random access procedure. Conversely, the second scheme
is to transmit the UE's unique identifier (e.g., S-TMSI or random ID) if
the UE has not received a valid cell identifier prior to the random
access procedure. In general, the unique identifier is longer than the
cell identifier. If the UE has transmitted data corresponding to the UL
Grant, the UE starts a contention resolution (CR) timer.

[0082](4) Message 4 Reception

[0083]After transmitting the data with its identifier through the UL Grant
included in the random access response, the UE waits for an indication
(instruction) from the eNode B for contention resolution. That is, the UE
attempts to receive the PDCCH so as to receive a specific message (S504).
Here, there are two schemes to receive the PDCCH. As described above, the
UE attempts to receive the PDCCH using its own cell identifier if the
message 3 transmitted in correspondence with the UL Grant is transmitted
using the UE's cell identifier, and the UE attempts to receive the PDCCH
using the temporary C-RNTI included in the random access response if the
identifier is its unique identifier. Thereafter, in the former scheme, if
the PDCCH is received through its own cell identifier before the
contention resolution timer is expired, the UE determines that the random
access procedure has been normally performed and completes the random
access procedure. In the latter scheme, if the PDCCH is received through
the temporary C-RNTI before the contention resolution timer has expired,
the UE checks data transferred by the PDSCH indicated by the PDCCH. If
the unique identifier of the UE is included in the data, the UE
determines that the random access procedure has been normally performed
and completes the random access procedure.

[0084]Hereinafter, the LTE system, by way of example, a uplink Hybrid
Automatic Repeat Request (HARQ) scheme of a MAC layer will be described,
concentrating on the transmission of uplink data.

[0086]A UE may receive UL Grant information or UL scheduling information
from an eNode B on a PDCCH (step S601), in order to transmit data to the
eNode B by the HARQ scheme. In general, the UL scheduling information may
include a UE identifier (e.g., a C-RNTI or a Semi-Persistent Scheduling
C-RNTI), resource block assignment, transmission parameters (modulation,
coding scheme and redundancy version), and a New Data Indicator (NDI). In
the LTE system, the UE has eight HARQ processes and the HARQ processes
are synchronously performed with Transmission Time Intervals (TTIs). That
is, specific HARQ processes may be sequentially assigned according to
points in time when data is received, in a manner of using the first HARQ
process at TTI 9 and using the second HARQ process at TTI 10 after a
first HARQ process is used at TTI 1, a second HARQ process is used at TTI
2, . . . , and an eighth HARQ process is used at TTI 8.

[0087]In addition, since the HARQ processes are synchronously assigned as
described above, a HARQ process connected to a TTI in which a PDCCH for
initial transmission of specific data is received is used for the
transmission of the data. For example, if it is assumed that the UE has
received a PDCCH including UL scheduling information at an Nth TTI,
the UE transmits data at an (N+4)th TTI. In other words, a Kth
HARQ process assigned at the (N+4)th TTI is used for the
transmission of the data. That is, the UE may transmit the data to the
eNode B on a PUSCH according to the UL scheduling information after
checking the UL scheduling information transmitted to the UE by
monitoring the PDCCH at every TTI (step S602).

[0088]When the data has been received, the eNode B stores the data in a
soft buffer and attempts to decode the data. The eNode B transmits an ACK
signal if the decoding of the data succeeds and transmits an NACK signal
if the decoding of the data fails. An example in which the decoding of
the data fails and the eNode B transmits the NACK signal on a Physical
HARQ Indicator Channel (PHICH) is shown in FIG. 6 (step S603).

[0089]When the ACK signal has been received from the eNode B, the UE
determines that the transmission of the data to the eNode B succeeds and
transmits next data. However, when the UE receives the NACK signal as
shown in FIG. 6, the UE may determine that the transmission of the data
to the eNode B has failed and retransmit the same data by the same scheme
or a new scheme (step S604).

[0090]The HARQ retransmission of the UE may be performed by a non-adaptive
scheme. That is, the initial transmission of specific data may be
performed when the PDCCH including the UL scheduling information should
be received, but the retransmission may be performed even when the PDCCH
is not received. In the non-adaptive HARQ retransmission, the data is
retransmitted using the same UL scheduling information as the initial
transmission at a TTI at which a next HARQ process is assigned, without
receiving the PDCCH.

[0091]The HARQ retransmission of the UE may be performed by an adaptive
scheme. In this case, transmission parameters for retransmission are
received on the PDCCH, but the UL scheduling information included in the
PDCCH may be different from that of the initial transmission according to
channel statuses. For example, if the channel status is better than that
of the initial transmission, transmission may be performed at a high bit
rate. In contrast, if the channel status is worse than that of the
initial transmission, transmission may be performed at a lower bit rate
than that of the initial transmission.

[0092]If the UE receives the UL scheduling information on the PDCCH, it is
determined whether data which should be transmitted at this time is data
which is initially transmitted or previous data which is retransmitted,
by an NDI field included in the PDCCH. The NDI field is toggled in the
order of 0, 1, 0, 1, . . . whenever new data is transmitted as described
above, and the NDI field of the retransmission has the same value as that
of the initial transmission. Accordingly, the UE may compare the NDI
field with the previously transmitted value so as to determine whether or
not the data is retransmitted.

[0093]The UE counts the number of times of transmission (CURRENT_TX_NB)
whenever data is transmitted by the HARQ scheme, and deletes the data
stored in the HARQ buffer when CURRENT_TX_NB has reached a maximum
transmission number set in an RRC layer.

[0094]When the retransmitted data is received, the eNode B attempts to
combine the received data and the data stored in the soft buffer due to
the failure of the decoding by various schemes and decodes the combined
data. The eNode B transmits an ACK signal to the UE if the decoding
succeeds and transmits an NACK signal to the UE if the decoding fails.
The eNode B repeats a process of transmitting the NACK signal and
receiving the retransmitted data until the decoding of the data succeeds.
In the example of FIG. 6, the eNode B attempts to combine the data
retransmitted in step S604 and the data which is previously received and
stored and decodes the combined data. The eNode B transmits the ACK
signal to the UE on the PHICH if the decoding of the received data
succeeds (step S605). The UE may transmit the UL scheduling information
for the transmission of next data to the UE on the PDCCH, and may
transmit the NDI toggled to 1 in order to report that the UL scheduling
information is not used for the adaptive retransmission, but is used for
the transmission of new data (step S606). The UE may transmit new data to
the eNode B on the PUSCH corresponding to the received UL scheduling
information (step S607).

[0095]The random access procedure may be triggered in the above-described
cases as described above. Hereinafter, the case where the UE requests UL
radio resources will be described.

[0096]FIG. 7 is a view illustrating a method of transmitting a message 3
in a random access procedure when UL radio resources are requested.

[0097]When new data is generated in a transfer buffer 601 of the UE, for
example, an RLC buffer and a PDCP buffer, the UE should generally inform
the eNode B of information about the generation of the data. More
accurately, when data having priority higher than that of data stored in
the transfer buffer of the UE is generated, the UE informs the eNode B
that the data is generated.

[0098]This indicates that the UE requests radio resources to the eNode B
in order to transmit the generated data. The eNode B may assign proper
radio resources to the UE according to the above information. The
information about the generation of the data is called a buffer status
report (hereinafter, referred to as "BSR"). Hereinafter, as described
above, the request for the transmission of the BSR is represented by
triggering of the BSR transmission (S6100). If the BSR transmission is
triggered, the UE should transmit the BSR to the eNode B. However, if the
radio resources for transmitting the BSR are not present, the UE may
trigger a random access procedure and attempt to request radio resources
(S6200).

[0099]As described above, if the random access procedure for requesting
the radio resources to the eNode B is triggered, the UE may transmit a
random access preamble to the eNode B and receive a random access
response message corresponding thereto as described with reference to
FIGS. 4 and 5. In addition, a message 3 (that is, a MAC PDU) including a
UE identifier and a BSR may be generated and stored in a Msg3 buffer 602,
in a MAC layer of the UE through a UL Grant signal included in the random
access response message. The message 3 stored in the Msg3 buffer 602 may
be copied and stored in a HARQ process buffer 603 indicated by the UL
Grant information. FIG. 7 shows, by way of example, the case where the
HARQ process A is used for the transmission of the message 3. Thus, the
message 3 is copied to the HARQ buffer 603 corresponding to the HARQ
process A. The message 3 stored in the HARQ buffer 603 may be transmitted
to the eNode B on a PUSCH.

[0100]Meanwhile, if the UE should perform retrial of the random access
procedure due to contention resolution failure, the UE may transmit the
random access preamble to the eNode B again and receive a random access
response (S6300). However, in the retried random access procedure, the UE
uses the message 3 stored in the Msg3 buffer 602 again, without
generating a new message 3. That is, the UE may copy and store the MAC
PDU corresponding to the message 3 stored in the Msg3 buffer 602 in a
HARQ buffer 604, and transmit the MAC PDU, according to the UL Grant
signal included in the random access response received in the retried
random access procedure. FIG. 7 shows the case where the reattempted
random access procedure is performed by a HARQ process B. The data stored
in the Msg3 buffer 602 may be copied into the HARQ buffer B and
transmitted.

[0101]As described above, if the random access response is received while
the random access procedure is performed, the UE stores the message 3
stored in the Msg3 buffer in the HARQ buffer and transmits the message 3.
As described above, in the current the LTE system standard for the HARQ
process, it is defined that the transmission of the data stored in the
Msg3 buffer is triggered by the reception of any UL Grant signal.
Accordingly, the CR timer may be erroneously driven such that an
erroneous contention resolution process is performed. Due to the
erroneous contention resolution procedure, the above-described BSR may
not be normally transmitted and the UE may come to deadlock. This problem
will be described in detail with reference to FIG. 8.

[0102]FIG. 8 is a view illustrating a problem which may occur when data
stored in a Msg3 buffer is transmitted by an Uplink (UL) Grant signal
received on a message other than a random access response message.

[0103]As described with reference to FIG. 7, the UE may trigger the BSR
when high priority data is generated, transmit the random access preamble
in order to transmit the BSR to the eNode B (S801), and receive the
random access response corresponding thereto (S802).

[0104]Thereafter, the UE may transmit a message 3 including the BSR via UL
Grant information included in the random access response message received
in step S802 (S803). If the message 3 is transmitted, the CR timer is
operated as described with reference to FIG. 5.

[0105]If the random access procedure is completed before the CR timer
expires, the UE determines that the random access procedure has not been
successfully completed (S804). In this case, the UE may try to restart
the random access procedure from the transmission of the random access
preamble.

[0106]At this time, since the eNode B does not yet know that the UE is
performing the random access procedure, the eNode B may transmit a UL
Grant signal independent of the random access procedure on a masked PDCCH
(S805). In this case, according to the current LTE system standard, the
UE transmits the message 3 stored in the Msg3 buffer according to the UL
Grant signal received on the PDCCH in step S805 (S806). In addition, when
the message 3 is transmitted, the CR timer is restarted. That is, even
when the UE does not perform the transmission of the random access
preamble and the reception of the random access response message, the CR
timer is restarted in step S806.

[0107]Although the CR timer is started as the UE transmits the message 3
in step S806, the eNode B may not know that the UE is performing the
random access procedure because the reception of the random access
preamble and the transmission of the random access response message are
not performed. If another UL Grant signal is received on the PDCCH
including the UE identifier (S807), the UE determines that the ongoing
random access procedure is successfully completed. Accordingly, the UE
may stop the ongoing CR time (S808).

[0108]If the message 3 transmitted to the eNode B in step S806 is not
successfully received by the eNode B (A), the UE no longer transmits the
message 3 including the BSR. Accordingly, if additional data is not
generated, the UE may not transmit the data generated in the transfer
buffer to the eNode B.

[0109]The above-described problem will be described as follows.

[0110]According to the current LTE system standard, if the UL Grant signal
is received in a state in which the data is stored in the Msg3 buffer,
the UE transmits the data stored in the Msg3 buffer to the eNode B. At
this time, the UL Grant signal may be transmitted by the eNode B, not for
the transmission of the data stored in the Msg3 buffer, but for the
transmission of other data. Accordingly, the CR timer may be erroneously
started.

[0111]In addition, if the eNode B does not know that the CR timer is
erroneously started in the UE and transmits the UL Grant signal for the
transmission of other data as described with reference to FIG. 8,
information (e.g., BSR) to be transmitted through the message 3 may be
lost.

[0112]In addition, the UE may not receive a message 4 for completing a
proper contention resolution procedure even with respect to the ongoing
random access procedure.

[0113]In a preferred embodiment of the invention for solving the
above-described problem, the data stored in the Msg3 buffer is
restrictively transmitted only in the case where the UL Grant signal
received from the eNode B is received on the random access response
message, but not in all cases where the UL Grant signal is received from
the eNode B. If the UL Grant signal is received on the masked PDCCH not
by the random access response message but by the UE identifier (C-RNTI or
a Semi Persistent Scheduling Radio Network Temporary Identifier
(SPS-RNTI)) in a state in which the data is stored in the Msg3 buffer, a
method of acquiring and transmitting new data (MAC PDU) to the eNode B
instead of the data stored in the Msg3 buffer is suggested.

[0114]FIG. 9 is a flowchart illustrating a method of transmitting UL data
by a UE according to a preferred embodiment of the present invention. In
more detail, FIG. 9 shows the operation of a HARQ entity of the UE
according to an embodiment of the present invention at every TTI.

[0115]First, the HARQ entity of the UE may identify a HARQ process
associated with a TTI (S901). If the HARQ process associated with the TTI
is identified, the HARQ entity of the UE may determine whether or not a
UL Grant signal received from the eNode B indicated at the TTI (S902).
The UE may determine whether or not a HARQ buffer corresponding to the
HARQ process is empty if there is no information about the received UL
Grant signal at the TTI, and perform non-adaptive retransmission as
described with reference to FIG. 6 if there is data in the HARQ buffer
(S903).

[0116]Meanwhile, if there is a UL Grant signal received from the eNode B
at the TTI, it may be determined (1) whether the UL Grant signal is not
received on the PDCCH indicated by the temporary C-RNTI and the NDI is
toggled from the value during transmission prior to the HARQ process, (2)
whether there is previous NDI and this transmission is initial
transmission of the HARQ process, (3) whether the UL Grant signal is
received on the PDCCH indicated by the C-RNTI and the HARQ buffer of the
HARQ process is empty, or (4) whether the UL Grant signal is received on
the random access response message (S904). If any one of the conditions
(1) to (4) is satisfied in step S904 (A), the method progresses to step
S906. In contrast, if any one of the conditions (1) to (4) is not
satisfied in step S904 (B), the method progresses to step S905 of
performing adaptive retransmission using the UL Grant signal (S905).

[0117]Meanwhile, the UE determines whether there is data in the Msg3
buffer in step S906 (S906). In addition, even when there is data in the
Msg3 buffer, the UE determines whether the received UL Grant signal is
received on the random access response message (S907). That is, the UE
according to the present embodiment transmits the data stored in the Msg3
buffer only when there is data in the Msg3 buffer when receiving the UL
Grant signal and the UL Grant signal is received on the random access
response message (S908). If there is no data in the Msg3 buffer when
receiving the UL Grant signal or the UL Grant is not received on the
random access response message, the UE determines that the eNode B makes
a request not for the transmission of the data stored in the Msg3 buffer
but for transmission of new data, and performs new data transmission
(S909). In more detail, the HARQ entity of the UE may be controlled such
that a MAC PDU including new data from a multiplexing and assembly entity
is acquired and is transmitted through the HARQ process.

[0118]Hereinafter, an example applied to a process of transmitting a BSR
by the UE which operates by the embodiment described with reference to
FIG. 9 as shown in FIG. 8 will be described.

[0119]FIG. 10 is a view illustrating a method of transmitting UL data when
a BSR is triggered in a UE, according to an embodiment of the present
invention.

[0120]As described above, new data may be generated in the RLC and PDCP
buffers of the UE. It is assumed that the generated new data has higher
priority than that of the data already stored in the RLC and PDCP
buffers. The UE may trigger the BSR transmission in order to inform an
eNode B of information about the generation of the data (step 1).

[0121]The UE should transmit the BSR according to BSR transmission
trigger, but, in a special case, there may be no radio resource for
transmitting the BSR. In this case, the UE may trigger a random access
procedure for transmitting the BSR. It is assumed that the random access
procedure triggered in the present embodiment is the contention based
random access procedure described with reference to FIG. 5.

[0122]The UE may transmit a random access preamble to the eNode B
according to the triggering of the random access procedure (step 2).

[0123]The eNode B may receive the random access preamble transmitted by
the UE and transmit a random access response message to the UE (step 3).
The UE may receive the random access response message.

[0124]The UE may generate a message 3 including the BSR and a UE
identifier according to a UL Grant signal included in the random access
response message received in step 3 and store the message 3 in a Msg3
buffer (step 4).

[0125]The UE may select a HARQ process according to the UL Grant
information included in the random access response message received in
step 3 and copy and store the message 3 stored in the Msg3 buffer in the
buffer corresponding to the selected HARQ process. Thereafter, the data
stored in the HARQ buffer may be transmitted to the eNode B according to
the UL HARQ procedure described with reference to FIG. 6 (step 5). The UE
starts (or restarts) the CR timer by the transmission of the message 3.

[0126]When the CR timer expires, the UE may perform retrial of the random
access procedure. That is, a random access preamble and a PRACH resource
may be prepared to be selected and transmitted to the eNode B. However,
in a state in which the CR timer is not operated, the UE may receive the
UL Grant signal from the eNode B on a PDCCH masked by a UE identifier
(step 6).

[0127]When the UL Grant signal has been received on the PDCCH in step 6,
the UE generates new data different from the data stored in the Msg3
buffer according to the UL Grant information received in step 6 as a new
MAC PDU, unlike the procedure of the embodiment of FIG. 8 for
transmitting the message 3 stored in the Msg3 buffer according to the UL
Grant information received in step 6 (step 7). In more detail, if the UE
receives the UL Grant signal in step 6 but does not receive the UL Grant
signal on the random access response message, a MAC PDU for transmitting
not the data stored in the Msg3 buffer but new data from a multiplexing
and assembly entity may be acquired and transmitted using a HARQ process
corresponding thereto.

[0128]After the new MAC PDU is generated, the UE according to the present
embodiment may select a HARQ process according to the UL Grant signal
received in step 6, store the MAC PDU newly generated in step 7 in the
buffer corresponding to the HARQ process, and transmit the MAC PDU to the
eNode B according to the UL HARQ procedure (step 8).

[0129]Thereafter, the UE may perform a random access procedure including
the transmission of the random access preamble and the reception of the
random access response and transmit the BSR stored in the Msg3 buffer to
the eNode B.

[0130]According to the above-described embodiment, it is possible to
prevent the eNode B from erroneously operating the CR timer due to the UL
Grant signal transmitted not for transmission of the data stored in the
Msg3 buffer but for transmission of new data. Accordingly, the problem
that the message 3 is lost may be solved. In addition, the random access
procedure of the UE with the eNode B may be normally performed.

[0131]Unlike the above-described embodiment, as another embodiment of the
present invention, a method of performing a process while ignoring the UL
Grant signal if the UL Grant signal is received from the eNode B on the
PDCCH masked by the UE identifier during the random access procedure of
the UE may be implemented. In this case, the UE may transfer the message
3 to the eNode B by the normal random access procedure, and the eNode B
may retransmit the UL Grant signal for the transmission of new data after
the random access procedure of the UE is completed.

[0132]Hereinafter, the configuration of the UE for implementing the
above-described embodiment of the present invention will be described.

[0133]FIG. 11 is a schematic view showing the configuration of a UE
according to an embodiment of the present invention.

[0134]As shown in FIG. 11, the UE according to the present embodiment may
include a reception (Rx) module 1101 for receiving a UL Grant signal from
an eNode B on a specific message, a transmission (TX) module 1102 for
transmitting data to the eNode B using the received UL Grant signal, a
Msg3 buffer 1103 for storing UL data transmitted in a random access
procedure, and a HARQ entity 1104 for controlling the transmission of UL
data of the UE.

[0135]In particular, the HARQ entity 1104 of the UE according to the
present embodiment performs a function of determining whether there is
data stored in the Msg3 buffer 1103 when the Rx module 1101 receives the
UL Grant signal and a function of determining whether the Rx module 1101
receives the UL Grant signal on a random access response message. If
there is data stored in the Msg3 buffer 1103 when the Rx module 1101
receives the UL Grant signal and the RX module 1101 receives the UL Grant
signal on the random access response message, the data stored in the Msg3
buffer 1103 is controlled to be acquired and transmitted to the eNode B.
If there is no data stored in the Msg3 buffer 1103 when the Rx module
1101 receives the UL Grant signal and the RX module 1101 receives the UL
Grant signal not on the random access response message but on the PDCCH,
the data stored in the Msg3 buffer 1103 is not transmitted but new data
is acquired from the multiplexing and assembly entity in the form of a
MAC PDU and is transmitted to the eNode B.

[0136]In addition, in order to perform the UL HARQ procedure, the UE
according to the present embodiment may include one or more HARQ
processes 1106 and HARQ buffers 1107 corresponding to the HARQ processes
1106. In the current LTE system, eight independent HARQ processes are
defined for use, but the present invention is not limited thereto.

[0137]Meanwhile, the HARQ entity 1104 according to the present embodiment
may transfer the data acquired from the multiplexing and assembly entity
1105 or the msg3 buffer 1103 to a specific HARQ process 1106 using the
above-described configuration, and control the specific HARQ process 1106
to transmit the data acquired from the multiplexing and assembly entity
1105 or the Msg3 buffer 1103 through the Tx module 1102. As described
above, if the specific HARQ process 1106 transmits the data stored in the
Msg3 buffer 1103 through the Tx module 1102 as described above, the data
stored in the Msg3 buffer 1103 may be copied into the specific HARQ
buffer 1107 corresponding to the specific HARQ process 1106 and the data
copied into the specific HARQ buffer 1107 may be transmitted through the
Tx module 1102.

[0138]At this time, the data stored in the Msg3 buffer 1103 is a MAC PDU
including a UE identifier and may further include information such as a
BSR according to the purpose of the random access procedure.

[0139]In the configuration of the UE shown in FIG. 11, the Tx module 1102
and the Rx module 1101 may be configured as a physical layer processing
module 1108, and the HARQ entity 1104, the multiplexing and assembly
entity 1105 and one or more HARQ processes 1106 may be configured as a
MAC layer module 1109. However, the invention is not limited thereto. In
addition, the Msg3 buffer 1103 and the HARQ buffers 1107 corresponding to
the HARQ processes 1106 may be implemented using any storage medium.

[0140]Although the signal transmission or reception technology and the UE
for the same are applied to a 3GPP LTE system, they are applicable to
various mobile communication systems having a similar procedure, in
addition to the 3GPP LTE system.

[0141]It will be apparent to those skilled in the art that various
modifications and variations can be made in the present invention without
departing from the spirit or scope of the invention. Thus, it is intended
that the present invention covers the modifications and variations of
this invention provided they come within the scope of the appended claims
and their equivalents.